Climate Change, Climate Variability and natural hazards Flashcards
What is climate change/ Variability
climate is the average weather at a given point and time of year, over a long period (30 yrs). We expect the weather to change a lot from day to day, but we expect the climate to remain relatively constant. If the climate doesn’t remain constant, we call it climate change. The key question is what is a significant change- and this depends upon the underlying level of climate variability. Crucial to understand the difference…
Climate change and variability according to the IPCC
IPCC (2007) finds that ‘warming of the climate system is unequivocal’ and ‘changes in the global climate system during the 21st cent..would be very likely be larger than those observed during the 20th cent. (>90% probability). IPCC makes no clear statement on changes in climate variability- we don’t know if it has changed or if it is likely to change in the future.
What is the el Nino-southern oscillation (ENSO)
The major mode of climate variability. It is naturally occurring and it is the interaction of the ocean-atmosphere in the tropical pacific.Winds, ocean temperatures, cloud and rainfall patterns all change. Occurs every 2-7 years, last 9-12 months (up to 2 years). Irregular. During a strong El nino, global temps can rise by 0.3 C. Impacts includes, coral bleaching due to high sea temps, peruvian fishing and sea bird movement, south american rainfall. droughts in Africa promotes fires. Modulates strength of Tropical storms. Increased convection to the center when el nino.
Does the ENSO affect hurricanes?
Yes- less Atlantic hurricanes in El Nino years.Thought to be mainly because high level winds increase, making it harder for hurricanes to form.
ENSO Impacts
The most famous impacts of el nino events are: damages from floods and landslides caused by very high rainfall in peru and southern california. Collapse of the Peruvian anchovetta fisheries because of warmer coastal waters. Forest fires in Indonesia that have caused serious air pollution problems. Crop failures and sometimes famine from droughts in southern africa
Enso and climate variability
Enso impacts are only a subset of the impacts of year to year global climate variability. At most ENSO may be responsible for about 50% of seasonal climate variability in some regions. In most regions of the world its influence is small or non-existent.
North Atlantic Oscillation (NAO)
Main expression of climate variability in NW Europe. Reflects strength of westerly winds off the Atlantic. NAO+ Mild, wet winder, NAO- cold, dry winter.
Summary of climate variability and its influence on natural hazards.
Climate always shows some level of natural variation- even without man-made climate change. ENSO is the major mode of Climate variability. ENSO clearly influences the distribution of drought, floods and hurricane activity. Understanding and predicting ENSO can be important for warnings of some hazards. NAO is a more important index of climate variability.
